TESTS ON ASPHALT MIX

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7.1 DETERMINATION OF RATE OF SPREAD OF BINDER (CUTBACK BITUMEN)

OBJECTIVE

• To determine the rate of spread of binder (cutback bitumen).

APPARTUS

• Balance of capacity 2kg and sensitivity 0.1gm.

• G.I trays of size 30 x 30 x 2.5cm 2 Nos.

• Kerosene or benzene.

PROCEDURE

• Record the base area (A) and the initial weight (W) of each tray.

• Place the trays on the spraying / tacking zones in such away that they are clear from the tyre

zone during run.

• As soon as the sprayer passes over the tray remove and record the final weight of the tray

(W1).

• Determine the net weight of the binder in each tray (W1-W).

• Make at least two determinations for each test.

CALCULATIONS

W1 – W• Rate of spread of binder = ---------------

AREPORT

• Report the individual and the mean results in kg/m2 to the nearest second decimal

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7.2 DETERMINATION OF BINDER CONTENT FOR ASPHALT MIX

STANDARD

• IRC: SP 11 –1988 (Appendix - 5), ASTM D 2172.

OBJECTIVE

• To determine the binder content in the asphalt mix by cold solvent extraction

APPARTUS

• Centrifuge

• Balance of capacity 500 gram and sensitivity 0.01grams.

• Thermostatically controlled oven with capacity up to 2500C.

• Beaker for collecting extracted material.

PROCEDURE

• Take exactly 500 grams of representative sample and place in the bowl of extraction

apparatus (W1).

• Add benzene to the sample until it is completely submerged.

• Dry and weigh the filter paper and place it over the bowl of the extraction apparatus

containing the sample ( F1 ) .

• Clamp the cover of the bowl tightly.

• Place a beaker under the drainpipe to collect the extract

• Sufficient time (not more than an hour) is allowed for the solvent to disintegrate the sample

before running the centrifuge.

Fig: 7.2.1 Bitumen Extractor.

• Run the centrifuge slowly and then gradually increase the speed to a maximum of 3600 rpm

• Maintain the same speed till the solvent ceases to flow from the drainpipe.

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• Run the centrifuge until the bitumen and benzene are drained out completely.

• Stop the machine, remove the cover and add 200ml of benzene to the material in the

extraction bowl and the extraction is done in the same process as described above.

• Repeat the same process not less than three times till the extraction is clear and not darker

than a light straw colour.

• Collect the material from the bowl of the extraction machine along with the filter paper and

dry it to constant weight in the oven at a temperature of 1050C to 1100C and cool to room

temperature.

• Weigh the material ( W2 ) and the filter paper ( F2 ) separately to an accuracy of 0.01grams.

CALCULATIONS

W1 – (W2 + W3)• Percentage of binder in the total mix = ---------------------- x 100 W1

W1 = Weight of sample taken

W2 = Weight of sample after extraction

W3 = Increased weight of filter paper ( F2 – F1 )

REPORT

• The result obtained shall be reported as the percentage of binder content in the mix to the

nearest second decimal.

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7.3 DETERMINATION OF ASPHALT MIX PROPERTIES

STANDARD

• MS-4 1989, ASTM D 1559 and AASHTO Designation: T 166 – 78.

OBJECTIVE

• To determine the properties of asphalt mix such as density, voids, stability and flow.

APPARATUS

• Marshal Testing Machine

• Compaction pedestal consisting of a 200x460x460mm wooden post capped with a

305x305x25mm steel plate.

• Compaction mould consisting of a base plate, forming mould and color extension. The

internal diameter of forming mould should be 101.60mm and a height of approximately

75mm.

• Compaction hammer consisting of flat circular tamping face 98.40mm diameter and

equipped with 4.50 Kilogram weight constructed to obtain a specified 457mm height of

drop.

• Mould holder consisting of a spring tension device designed to hold compaction mould in

place on compaction pedestal.

• Pans, metal, round, approximately 4 liters capacity for mixing of asphalt and aggregates.

• Thermostatically controlled oven and electrical hot plate.

• Scoop, mixing spoon, trowel and spatula.

• Mechanical mixer (optional) of 4lits capacity equipped with two metal mixing bowls and

two wire stirrers.

• Thermostatically controlled water bath

• Gloves and welders for handling hot equipment.

• Marking crayons.

• Extrusion jack for extruding compacted specimens from mould.

• Balance of capacity 10 kg’s and sensitivity 0.5 gms and of such a type and shape so as to

permit the basket containing the sample to be suspended from the beam and weighed in

water.

• Wire basket of not more than 6.3mm mesh or a perforated container of convenient size

preferably chromium plated and polished, with wire hangers thickness not less than 1mm.

• A stout watertight container in which the basket may be freely suspended

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• Two dry soft absorbent clothes each not less than 650 cm2

PROCEDURE

• Prepare test specimens either from Laboratory mix or from plant mix or from paved surface.

Preparation of Mix in the Laboratory

• Take representative sample of aggregates and dry to constant weight at 1050 to 1100C.

• Separate the aggregates by dry sieving in to desired size of fraction.

• Weigh in to separate pans for each test specimen the amount of each size of fraction

required to produce a batch that will result in a compacted specimen of height 63.5 + 1.3

mm which is generally of 1.20kg including asphalt percentage.

• It is generally desirable to prepare a trial specimen prior to preparing aggregate batches.

• If the trial specimen height falls out side the limits, the amount of aggregate used for the

specimen may be adjusted as follows

63.50 (Mass of aggregate used)Adjusted mass of aggregate = -------------------------------------------

Specimen height (mm) obtained

• Place the pans in the oven or on the hot plate and heat the aggregates to a temperature of

approximately 280C above the mixing temperature

• Heat the asphalt cement to a temperature not more than 1600C.

• Charge the mixing bowl with heated aggregates and dry mix thoroughly.

• From a carter in the dry blended aggregates and weigh the required amount of asphalt

cement in to the mixture accordance with the accumulative batch weights.

• The temperature to which the asphalt must be heated to produce viscosity of 170 + 20

centistokes shall be taken as the mixing temperature.

• Care shall be taken to maintain temperature of aggregates and asphalt cement be with in the

limits of the mixing temperature.

• Mix aggregates and asphalt cement, preferably with a mechanical mixer or by hand with a

trowel as quickly and thoroughly as possible to yield a mixture having a uniform

distribution of asphalt through out.

Determination of Compacting Temperature

• The temperature to which the asphalt must be heated to produce viscosity of 280 + 30

centistokes shall be taken as the compacting temperature.

Preparation of Mould and Hammer

• Thoroughly clean the mould assembly and heat the face of the compaction hammer in a

boiling water bath or on the hot plate to a temperature between 930C and 1490C.

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Compaction of Specimens

• Place a piece of waxed paper cut to size in the bottom of the mould before the mix is placed

in the mould.

• Place the entire batch in the mould.

• Spade the mix vigorously with a heated spatula or trowel 5 times round the perimeter and 10

times over the interior.

• Remove the collar and smoothen the surface to a slightly rounded shape.

• The temperature of the mix immediately prior to compaction shall be with in the limits of

the compaction temperature.

• Replace the collar, place the mould assembly on the compaction pedestal in the mould

holder.

• Apply either 35,50 or 75 blows as specified according to the design traffic category with the

compaction hammer using a free fall of 457mm. Hold the axis of the compaction hammer as

nearly perpendicular to the base of the mould assembly during compaction as shown in

Fig: 7.3.1.

• Remove the base plate and collar, reverse and reassemble the mould.

• Apply the same number of compaction blows to the face of the reversed specimen.

• After compaction, remove the base plate and allow the specimen to cool in air until no

deformation will result while removing it from the mould.

• Remove the specimen from the mould by means of extrusion jack and then place on a

smooth level surface until ready for testing.

Fig: 7.3.1 Casting of Marshall specimens.

• Marking shall be done on the specimens for identification.

• Leave the specimens to cool over night.

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• In the Marshall Method each compacted specimen is tested to determine the following

properties

Density and Voids Analysis

Stability and Flow

Density and Voids Analysis

• The bulk density test be may be performed as soon as the freshly compacted specimens are

cooled to room temperature (AASHTO Designation: T 166 - 78)

• There are two methods for the determination of bulk density

• Bulk density of compacted specimens with Paraffin coating

• Bulk density of compacted specimens on saturated surface dry basis

Bulk density of Paraffin coated Specimen

• Record the mass of the uncoated specimen to an accuracy of 0.5 grams (A).

• Coat the test specimen on all surfaces with melted paraffin sufficiently thick to seal all

surface voids.

• Application of the paraffin may be accomplished by chilling the specimen in a refrigerating

unit to a temperature of approximately 4.50C for 30min at then dipping the specimen in

warm paraffin (5.50C above matching).

• It may be necessary to brush the surface of the paraffin with added hot paraffin in order to

fill any pinpoint holes.

• Allow the coating to cool in air at room temperature for 30min and then weigh (D) the

specimen.

• Weigh the paraffin coated specimen (E) in water bath at 25+ 10 C.

• Determine the Specific Gravity of Paraffin at 25 + 10 C if unknown and designate this as F.

A• Bulk Density = ----------------------------------

D - A D - E - ---------

FA = Mass of dry specimen in air

D = Mass of paraffin coated specimen in air

E = Mass of paraffin coated specimen in water

F = Specific gravity of paraffin

Bulk Density of Compacted Specimens on Saturated Surface Dry Basis

• Record the mass of the specimen (A) to an accuracy of 0.5 grams.

• Record the mass of the specimen (C) in water at 25 + 10 C

• Remove the specimen from the water, surface dry by blotting with damp towel and

determine the surface dry mass (B).

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A• Bulk Density = -------

C - B A = Mass of specimen in air

B = Mass of specimen in water

C = Mass of surface dry specimen in air

Voids Analysis

• For the calculation of voids initially calculate the theoretical specific gravity of the

aggregates (Gt1) and the theoretical specific gravity of the mix (Gt).

100 ---------------------------

Theoretical specific gravity of the aggregates (Gt1) = W1+ W2 + W3 +W4 G1 G2 G3 G4

W1, W2 , W3 and W4 = Percentages of the aggregate.

G1, G2, G3andG4 = Specific gravity of the aggregate.

100Theoretical specific gravity of the mix (Gt) = --------------------------------------------------------

100 - % of bitumen - % of bitumen Gt1 spgr .of bitumen

• Calculate the Voids from the equations given below

% of bitumenVolume of bitumen (Vb) = Gb x --------------------------------------

Specific gravity of bitumen

Gt - GbAir voids (Vv) = ------------x100

Gt

Voids in mineral aggregate (VMA) = Vv + Vb

100 VbVoids filled with bitumen (VFB) = ---------------

VMAGb= Bulk density of the specimen.

Stability and Flow

• Immerse the test specimens in a water bath maintained at 600C + 10C for 30 to 40 minutes

before commencing the test.

• Thoroughly clean the inside surface of the testing head.

• Temperature of the testing head shall be maintained within 210C to 37.800C using a water

bath whenever required.

• Lubricate guide rods with a thin film of oil so that upper test head will slide freely without

binding.

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• Check the dial indicator of the dial gauge to be firmly fixed and set to zero load position.

• With testing apparatus ready, remove test specimen from water bath and carefully wipe the

surface.

• Place the specimen in the lower testing head and center, and then fit the upper testing head

into position and center complete loading device.

• Place flow meter over marked guide rod and set the needle to zero.

• Apply load on the specimen at the constant rate of deformation 51mm per minute.

• The point of failure is defined by the maximum load reading obtained.

• Maximum load taken by the specimen at 600C shall be recorded as its Stability value.

Fig: 7.3.2 Testing of Marshall specimen.

• Note the flow meter reading immediately when the load begins to decrease in load meter.

• This reading is the flow value of the specimen, expressed in units of 0.25mm.

• The entire procedure, both Stability and Flow tests, starting with removal of specimen from

the water bath and testing shall be completed within a period of 30 seconds.

• Measured Stability values for specimens that depart from the standard 63.50mm thickness

shall be converted to an equivalent 63.50mm value by means of conversion factor from the

Table: 7.3.1.

• Average the flow values and the converted Stability values for all specimens.

Table: 7.3.1 Stability Correlation Ratios

Thickness of specimen, in mm Correlation Ratio

58.70 1.1460.30 1.0961.90 1.0463.50 1.0064.00 0.9665.10 0.93

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66.70 0.89

68.30 0.86

Note*

The measured stability of a specimen multiplied by the correlation ratio for the specimen

thickness equals the corrected stability for a 63.50 mm specimen.

REPORT

• Report all the test results density, voids, stability and flow in a typical format.

PRECAUTIONS

• In no case shall the mix be reheated if the temperature falls down the specified limits of

compacting temperature.

• When more rapid cooling of moulds is desired table fans might be used but not water unless

the specimen is in water bags.

• Asphalt should not be at mixing temperature for more than one hour before using.

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7.4 SWELL TEST

STANDARD

• MS-4 1989

OBJECTIVE

• To determine the swelling of the compacted specimen under specified conditions of the test.

APPARTUS

• Mould of height 127mm and inside diameter 101.6mm tripod of height 170mm suitable to

fix for the mould of 101.6mm diameter.

• Dial gauge sensitivity to 0.025mm.

• Deep aluminum pan of size 194mm x 64mm

• Perforated bronze plate with adjustable stem.

• Graduated scale capable of reading up to 1mm.

PROCEDURE

• Compact the asphalt mix in to the mould as specified in MS-4 1989

• Allow the mould to cool at room temperature for at least one hour (This is done to permit

rebound after compaction).

• Place the mould and the specimen in the aluminum pan.

• Place a perforated bronze disc on the top of the specimen.

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Fig: 7.4.1 Swell Test

• Position tripod on the mould with dial gauge reading 2.54mm.

• Introduce 500ml of water in to the mould and measure distance (H) from top of the mould to

the top of the water with a graduated scale and keep the set up undisturbed for 24 hours.

• After 24 hours again read dial gauge (R1) and record the change.

• Also measure the distance (H1) from top of the mould to the top of the water with graduated

scale and record the change as permeability or the amount of water in millimeters that

percolates in to and / or through the test specimen.

CALCULATIONS

R1 – R• Swelling, (%) = -------------

RR = Initial dial gauge reading

R1 = Final dial gauge reading

• Permeability = H - H1

H = Initial height of water from the top of the mould

H1 = Final height of water from the top of the mould

REPORT

• Report the amount of swelling to the nearest second decimal and permeability to the nearest

1mm.

PRECAUTION

• Do not disturb the specimen during the period of swelling.

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7.5 DETERMINATION OF DEGREE OF COMPACTIONOF BITUMINOUS PAVEMENTS

STANDARD

• AASHTO Designation: T 230 - 68 (1974).

OBJECTIVE

• To determine the degree of pavement compaction of bituminous aggregate mixtures by

coring with diamond bit core drill as related to standard specimens compacted of the same

materials.

APPARTUS

• Diamond bit core drill machine

• Rigid plate or suitable container larger enough to hold the sample with out distortion after it

is removed from the pavement.

• Balance of capacity 10 kg’s and sensitivity 0.05 gms and of such a type and shape as to

permit the basket containing the sample to be suspended from the beam and weighed in

water.

• Wire basket of not more than 6.3mm mesh or a perforated container of convenient size

preferably chromium plated and polished, with wire hangers thickness not less than 1mm.

• A stout watertight container in which the basket may be freely suspended

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• Two dry soft absorbent clothes each not less than 650 cm2

PROCEDURE

Preparation of Standard Specimens

• Prepare standard specimens from the representative sample of mix to be tested for

compaction in accordance with MS-4 1989.

Determination of Bulk Density

• Determine the bulk density of the standard specimen in accordance with

AASHTO Designation: T 166 – 78.

Core cutting

• Use 100mm diameter core bit if the maximum nominal size of aggregate is 25mm or less

and 150 mm diameter core bit if the maximum nominal size of aggregate is over 25mm.

• Core a sample from the pavement and remove it carefully with out distorting, bending,

cracking or in away changing its physical condition as it was before removal from the

pavement.

• Forward the sample to the laboratory where it is to be tested.

• If there is any delay in forwarding the sample to the laboratory place the sample in a safe

and cool place.

• Submit complete identification information with the sample.

• Record the dimensions of the core in the laboratory.

Determination of Bulk Density

• Determine the bulk density of the core in accordance with AASHTO Designation: T166-74.

Degree of Pavement Compaction

• Determine the degree of pavement compaction by dividing the bulk density of pavement

specimen by the bulk density of standard specimen.

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Figure: 7.5.1 Coring of pavement layer.

CALCULATIONS

Bulk density of pavement specimen• Degree of compaction = ----------------------------------------------- x 100

Bulk density of standard specimen

REPORT

• Report all the values as the percentage of compaction to the nearest second decimal.

PRECAUTION

• Remove the core carefully with out distorting bending or in anyway changing its physical

condition as it was before removal from the pavement.

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